package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.Objects;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

@Slf4j
@Component
public class CacheClient {
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate){
        this.stringRedisTemplate = stringRedisTemplate;
    }

    public void set(String key, Object value, Long time, TimeUnit unit){
        stringRedisTemplate.opsForValue().set(
                key,
                JSONUtil.toJsonStr(value),
                time,
                unit);
    }

    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit){
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));

        stringRedisTemplate.opsForValue().set(
                key,
                JSONUtil.toJsonStr(redisData)
        );
    }

    public <R, ID> R queryWithPassThrough(
            String keyPrefix,
            ID id,
            Class<R> type,
            Function<ID, R> dbFallback,
            Long time,
            TimeUnit unit) {

        String key = keyPrefix + id;
        //1、从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);

        //2、判断是否存在
        if (StrUtil.isNotBlank(json)){
            //3、存在，直接返回
            return JSONUtil.toBean(json, type);
        }
        if (Objects.equals(json, "")){
            return null;
        }

        //4、不存在，根据id查询数据库
        R r = dbFallback.apply(id);

        //5、数据库中不存在，返回错误
        if (r == null){
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(
                    key,
                    "",
                    RedisConstants.CACHE_NULL_TTL,
                    TimeUnit.MINUTES);

            return null;
        }

        //6、存在，写入redis
        stringRedisTemplate.opsForValue().set(
                key,
                JSONUtil.toJsonStr(r),
                time,
                unit);
        return r;
    }

    public <R, ID> R queryWithLogicalExpire(
            String keyPredix,
            ID id,
            Class<R> type,
            Function<ID, R> dbFallback,
            Long time,
            TimeUnit unit) {
        //1、从redis查询商铺缓存
        String key = keyPredix + id;
        String json = stringRedisTemplate.opsForValue().get(key);

        //2、判断是否存在
        if (StrUtil.isBlank(json)){
            //3、存在，直接返回
            return null;
        }

        //4、命中，需要先把json反序列化成对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        JSONObject data = (JSONObject) redisData.getData();
        R r = JSONUtil.toBean(data, type);
        LocalDateTime expireTime = redisData.getExpireTime();

        //5、判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())){
            //5.1、未过期，直接返回店铺
            return r;
        }

        //5.2、过期，需要缓存重建
        //6、缓存重建
        //6.1、获取互斥锁
        String lockKey = RedisConstants.LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        //6.2、判断是否获取成功
        if (isLock){

            json = stringRedisTemplate.opsForValue().get(key);
            redisData = JSONUtil.toBean(json, RedisData.class);
            expireTime = redisData.getExpireTime();

            if (expireTime.isAfter(LocalDateTime.now())){
                //6.2.1、未过期，直接返回店铺
                return r;
            }

            //6.3、成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                //重建缓存
                try {
                    R r1 = dbFallback.apply(id);
                    this.setWithLogicalExpire(key, id, time, unit);
                }catch (Exception e){
                    throw new RuntimeException(e);
                }finally {
                    unlock(lockKey);
                }
            });
        }
        //6.4、返回过期的店铺信息
        return r;
    }

    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }
}
